The steering systems on many older vehicles are of antiqued design and have poor performance compared with modern steering systems. Owners of such older vehicles, seeking to improve steering performance, may replace original equipment steering systems, such as steering boxes, with better performing, more reliable systems such as rack and pinion steering systems.
When replacing a steering box with a rack and pinion steering system, the vehicle must support the rack and pinion system which typically extends between the vehicle's outer tie rods and is coupled via a linkage to the vehicle's steering wheel. A replacement rack and pinion system typically includes pivoting inner tie rods extending from a center housing that encloses the rack and pinion gearing. The rack is disposed inside the housing and is moved along its longitudinal axis by the pinion gear, which is coupled to the vehicle steering system. The inner tie rods of the replacement rack and pinion system thread into outer tie rods of the vehicle steering system such that as the pinion gear is rotated by the steering wheel, the rack moves longitudinally in one direction thereby moving the inner and outer tie rods and turning the vehicle wheels.
In body-on-frame vehicles, the vehicle body, engine, drive train, braking, steering and suspensions systems are bolted to the frame. The frame includes frame rails and frame cross members which are welded together, much like a ladder. The frame rails are generally parallel steel channels that extend substantially the length of the vehicle along opposite sides of the vehicle and are generally rectangular in cross section.
In unibody vehicles, by contrast, the body and frame are integrated and formed of a single stamping. A unibody vehicle does not have a separate frame, rather the unibody frame includes reinforced support points for mounting the engine, transaxle and other vehicle systems. Specifically, most vehicles with unibody construction include parallel front suspension mounting supports that support the front wheels and the front wheel suspension and steering systems. Some vehicles are a hybrid between unibody construction and body-on-frame construction having a unibody body and a partial or sub-frame that comprises the front suspension mounting supports. As used herein, the term “frame rails” will refer both to the parallel front suspension mounting supports of unibody and hybrid vehicles as well as the forwardly extending frame components that support the front wheels and front suspension systems of body-on-frame vehicles.
Using U-bolts to couple the rack and pinion housing to the frame rails is undesirable because the rack and pinion system becomes part of the vehicle suspension system, essentially becoming a cross member that extends between the frame rails. Flexing of the frame rails as the car is driven subjects the rack and pinion housing to stress, stain and shear forces. Since the rack and pinion system is not engineered to be a suspension member, such use typically leads to poor performance and/or premature failure of the rack and pinion steering system.
A more sophisticated method of supporting a replacement rack and pinion steering system involves mounting the rack and pinion housing to a support cradle and, in turn, mounting the cradle to one or both of the frame rails. Unfortunately, because vehicles designed with a steering box did not envision mounting of a cradle between the front suspension mounting supports, providing clearance for the rack and pinion system and the cradle supporting it is problematic. Because of clearance considerations, prior art cradles typically required cutting/removal of a suspension cross member to make room for the rack and pinion system and the cradle. Obviously, cutting/removal of a suspension member is a major disadvantage both from a performance perspective and from a vehicle resale position. Many potential purchasers of older, vintage vehicles are willing to pay a premium for vehicles that have not been modified, that is, that are in original condition. Thus, vehicle owners who install a replacement steering system for improved performance often want the option of being able to reinstall the original steering system and return the vehicle to its original condition for resale purposes.
Other prior art cradles required either drilling cradle mounting holes into the front suspension mounting supports or welding the cradle to the front suspension mounting supports or a hanger from the mounting supports. Again, this approach has major disadvantages in requiring permanent alteration of the vehicle suspension along with the difficulty and cost attendant with drilling holes in or welding the suspension mounting supports.
What is needed is a replacement steering assembly including a support cradle for properly supporting the replacement steering system and isolating it from the forces transmitted through the vehicle suspension system. What is also needed is a replacement steering assembly including a support cradle that does not require any welding, drilling or other permanent alteration of the vehicle upon installation of the cradle. What is also needed is a replacement steering assembly including a support cradle that does not require any cutting/removal of vehicle suspension members. What is also needed is a replacement steering assembly that is easy to install.